At 13.35 hours on 11 Sep 1939 the unescorted Firby (Master Thomas Prince) was attacked by U-48 with gunfire about 270 miles west of the Hebrides. After five hits the crew abandoned ship and the ship was sunk at 15.40 hours by one torpedo. The master and 33 crew members were picked up by HMS Fearless (H 67) (Cdr K.L. Harkness) and landed at Scapa Flow on 12 September.

After sinking this vessel, Schultze sent the following radio message:Transmit to Mr. Churchill. I have sunk British steamer Firby position 59°40N/13°50W. Save the crew if you will please. German submarine.The message was relayed by the American merchant Scanpenn and received by the Admiralty at Rosyth at 18.25 hours.